Birth Control Pills, Progestin-Infused IUDs and Progestin-Containing “Mini-pills” May Raise Breast Cancer Risk

Defective Drugs
Birth Control and Breast Cancer

By Lynn Shapiro, Staff Writer

A new study examining the risks associated with the current generation of hormonal contraceptives--including birth control pills containing estrogen and progesterone, progestin-infused IUDs, and progestin-containing “mini-pills”--- found that women who use these products face a small but significant breast cancer risk, according to a study published in the New England Journal of Medicine on December 7th.

Researchers followed approximately 1.8 million Danish women starting in 1995, comparing those who purchased hormonal birth control products with women who later developed breast cancer.

For every 100,000 women using hormonal birth control, consisting of both estrogen and progesterone, there were 68 cases of breast cancer annually, compared with 55 cases a year among non-users, a small but significant risk, Lina Morch of the University of Copenhagen reported in the New England Journal of Medicine study.

Earlier clinical trials have shown the same breast cancer risk for older versions of birth control pills used in the 1980’s.

Progestins are Problematic

The growing use of progestin-infused IUD’s, and progesterone-containing mini-pills is of concern, given the Danish study’s findings that women who used an IUD that releases progestin faced a 21 percent increase in risk for breast cancer, compared to nonusers.

Data gathered in the landmark Woman’s Health Initiative (WHI) study, started in 1991, support the finding that progestins are a primary trigger for breast cancer.

The WHI trial included 27,347 women ages 50-79 and was split into two groups of post-menopausal women: those who had undergone hysterectomies and were able to use estrogen-alone therapy; and those with their uteruses intact, who required combination estrogen and progesterone hormone replacement therapy.

Estrogen is said to promote uterine cancer, while progesterone protects against it. Progestin is a synthetic form of progesterone.

WHI Combination Therapy Trial Halted

The WHI estrogen-plus-progesterone trial, financed by the National Institutes of Health, was halted in July 2002, after investigators found:

  • Women who took estrogen plus progesterone were more likely to be diagnosed with breast cancer than those using a placebo.
  • The rate of death from breast cancer among those taking estrogen plus progestin birth control pills was 2.6 per 10,000 women per year, compared with 1.3 per 10,000 women per year among those taking the placebo.

The WHII study found no increased risk of breast cancer with estrogen alone

Older Women, Greater Risk

Older women suffer more breast cancer than younger women, and might consider switching to a non-hormonal birth control method, such as a non-hormonal IUD, a diaphragm or condoms.

On the plus side, oral contraceptives are associated with reductions in ovarian and endometrial cancers; and may lower the risk of colon cancer. 

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